Hong Kong conglomerate CK Hutchison said on Thursday it has filed international arbitration proceedings against Panama over its cancellation of a concession to operate two ports in the Panama Canal.

The dispute stems from a Panama supreme court ruling in January that struck down the contract that let Panama Ports Company (PPC), a unit of CK Hutchison, manage the canal’s Pacific port of Balboa and the Atlantic port at Cristobal.

The decision came after claims by US President Donald Trump that China effectively ran the canal, part of broader tensions between Washington and Beijing.

On Thursday, the company said it had launched international arbitration proceedings against Panama over “breaches of an investment protection treaty” that culminated in the cancellation of the concession and takeover of the two ports.

“The Company is seeking damages of more than US$1.5 billion for the destruction of the Company’s investments in Panama,” the firm’s board of directors said in a filing to the Hong Kong Stock Exchange.

“The Board strongly disagrees with the measures taken by Panama in violation of the treaty. The Company will continue to seek resolution with Panama while pursuing to the utmost all of the Company’s rights and remedies under the treaty and international law.”

Its subsidiary Panama Ports Company had filed a lawsuit opposing the suspension of its Panama Canal operations in February, and announced a month later it was seeking at least US$2 billion in damages.

The PPC will continue to pursue its own distinct rights under the separate arbitration, the board added.

The Panama Canal, which connects the Atlantic and Pacific oceans, handles about 40 percent of US container traffic and five percent of world trade.